Planning for decommissioning of oil and gas facilities should include assessment of contaminants of concern (COCs) like mercury, arsenic, and naturally occurring radionuclides. This allows for complete decontamination of equipment and removal of over 95% of COCs to ensure safe handling. Assessment of COCs throughout the production process can help predict costs and inform decommissioning strategies. Spent chemicals from decontamination must also be processed or disposed of properly to minimize hazardous waste.

1. August 2017 | EPmag.com
Ron Radford, ISCT Group US LLC
With costs for decommissioning nearing an all-
time low there is a choice that needs to be made
between spending today’s money today to capitalize on
low decommissioning service costs or spending tomor-
row’s money tomorrow when it is likely that with higher
oil prices there will be a redirection of assets toward new
E&P projects.
Asset managers argue over the optimal timing for per-
forming required decommissioning. However, during
the Society of Petroleum Engineering’s (SPE) “Asset
Abandonment: Emerging Reality” workshop held in
Kuala Lumpur in October 2016, decommissioning was
described as adding value to the business, should be fac-
tored into the asset’s life-cycle costs and should begin at
least three years before cessation of well operations.
As encouraging as that may be, further complicating
the economics of decommissioning is the potential
impact of contaminants of concern (COCs) on the pre-
dictability of decommissioning costs on a larger scale.
Anticipating costs begins with accurate measurements
of COCs in the reservoir and the deposition of these
COCs in the oil and gas processing stream.
Assessment of COCs such as mercury, arsenic and
naturally occurring radionuclides comes with technical
challenges but is required for complete facility and
process design and, ultimately, economic end-of-life
planning. Anticipation and quantification of volatile
metal COCs like mercury and arsenic require intuition
gained from experience in conjunction with continued
sampling and analysis throughout the process to build a
meaningful dataset along with computational modeling.
Adverse effects of COCs
The problem is greater than just leaving a little mercury
and arsenic behind in the process equipment. Most
governments seek to actively reduce anthropogenic
mercury discharges to the environment, including those
associated with hydrocarbon production and processing.
Identifying the adverse effects of COCs on impacted
equipment involves understanding what materials and
equipment are potentially susceptible, the distribution
of COCs throughout the process and the circumstances
that lead to degradation.
Another key consideration is the long-term risk to
human health and the environment. Mercury is consid-
ered a persistent, bioaccumulative and toxic substance.
Just “a little mercury” is hardly the case in subsea pipe-
lines and topside process equipment in Asia, where mass
loading rates can range from 5 µg/sq m to more than
100 µg/sq m. Some systems can have more than 1,000
kg of mercury either condensed as elemental or com-
plexed into the grain boundary and substrate of carbon
and stainless steel systems (adsorbed and chemisorbed).
Metal alloys used in production and processing systems
should be decontaminated such that complete COC
mass removal (more than 95%) is the primary objective,
thus assuring that components can be safely handled by
the end user (e.g., sent to a metals recycling facility or
deployed in a rigs-to-reef program). Calling for complete
removal is based primarily on the lack of uniform regula-
tions regarding acceptable residual COC concentrations.
Dealing with hazardous materials
in decommissioning
Planning and collaboration help ensure smart, safe handling of
COCs during facility decommissioning.
Decontamination of metal alloys used in production and
processing systems for complete COC mass removal should
be a primary objective for safe handling by end users.
(Source: Adam Gregor, Shutterstock.com)
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AUGUST 2017

2. Assessment for key COCs (mercury, arsenic or naturally
occurring radioactive material) may not be common prac-
tice in all areas. If left contaminated, the equipment may
require costly handling by a third-party disposal or decon-
tamination contractor, with little residual value of the recy-
cled asset recovered. This puts operators, decommission-
ing services firms and metals recycling facilities at risk.
Complete decontamination
The inclusion of assessment and distribution studies
into the decommissioning preplanning stage helps
ensure complete decontamination of the tubing, flow-
lines and topsides processing facilities offshore. The
technology required for this has been in development
for a decade and has been in full-scale use for two years
on the North West Shelf of Australia and in Asia.
Depending on data provided from characterization
or assumptions from surrogates, some hydrocarbon
process systems and equipment might require a phased
chemical cleaning approach using multiple chemistries
at various temperatures, residence times and flow rates.
ISCT designs each chemical decontamination phase
to incorporate temperature, residence times and sur-
face contact effects for the impacted systems. These
design parameters are critical components of a suc-
cessful decontamination strategy and are based on the
mass, depth profile and distribution of contaminants
throughout the systems.
Some categories of wastes cannot be exported due to
the Basel Convention on the Control of Transboundary
Movements of Hazardous Wastes and Their Disposal
Treaty. Also, because the costs to dispose of small volumes
can be high on a unit weight basis, processing spent chem-
ical decontamination fluids and materials is often the only
solution for a cost-effective decontamination program.
This provides planners a way of estimating costs based on
data, production and geographic final disposition.
Spent chemistry generated from the decontamination
action must be disposed of, processed or reinjected.
Disposal without processing (waste minimization) will
result in large quantities of hazardous waste or highly
reactive material that does not meet discharge crite-
ria. Processing COCs must be considered during pre-
planning to capture costs and develop comprehensive
decommissioning strategies.
There are few disposal options for high-concentration
waste streams regulated under the Basel Convention,
underscoring the importance of materials processing. It
makes the most sense to reinject spent production chem-
istries downhole in the well or in monitored injection
wells where limited processing is required for pH adjust-
ment and percentage of total suspended solids.
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